I think we're in danger of reading too much into the statement by Doyle that he can't believe Bodie's dead. Surely he's saying it in the same vein as someone saying ' he can't possibly be dead, I would know !' i.e. he doesn't mean it literally but is expressing his shock and hope against hope that Bodie's *not* dead. And likening it to Gabe's faith in God shows that it *is* just Doyle's faith rather than something more secular like any claim to knowledge or proof.